Led array module

ABSTRACT

The invention describes a light emitting diode array module (30) comprising a plurality of light emitting diode structures (10a, 10b), wherein the light emitting diode structures (10a, 10b) are arranged such that there is an optical cross talk between the light emitting diode structures (10a, 10b) during operation of the light emitting diode array module (30), wherein at least a first light emitting diode structure (10a) of the plurality of light emitting diode structures (10a, 10b) is characterized by a first color, and wherein at least a second light emitting diode structure (10b) of the plurality of light emitting diode structures (10a, 10b) is characterized by a second color different than the first color, wherein the first color, the second color and the optical cross talk between the light emitting diodes are arranged to provide a predefined light distribution in a reference plane (40) perpendicular to an optical axis (50) of the light emitting diode an-ay module (30). The invention further describes a lighting device comprising one or more LED array modules (30).

FIELD OF THE INVENTION

The invention relates to a light entitling diode (LED) array module. Theinvention further relates to a lighting device comprising one or moreLED array modules.

BACKGROUND OF THE INVENTION

The human eye is very sensitive with respect to variations in a lightdistribution or illumination pattern provided by a light source.Homogeneity of the correlated color temperature of the lightdistribution provided by a lighting module is therefore an importantquality criterion. Especially lighting modules comprising a multitude oflight emitters like light emitting diode (LED) structures require acareful selection of these LED structures in order to enable ahomogeneous distribution of the color and especially of the correlatedcolor temperature in a defined sector of the space illuminated by thelighting modules.

US 2012/0106145 A1 discloses an operating light which includes at leastone first radiation source, which is suitable for producing light withlocally different, especially radially outwardly decreasing colortemperature distribution in a plane extending at right angles to thework area.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light emittingdiode (LED) array module with improved distribution of the colorespecially the correlated color temperature.

The invention is described in the independent claims. The dependentclaims comprise preferred embodiments.

According to a first aspect a light emitting diode (LED) array module isprovided, The LED array module comprises a plurality of light emittingdiode structures. The light emitting diode structures are arranged suchthat there is an optical cross talk between the light emitting diodestructures during operation of the light emitting diode array module. Alleast a first light emitting diode structure of the plurality of lightemitting diode structures is characterized by a first color or flux. Atleast a second light emitting diode structure of the plurality of lightemitting diode structures is characterized by a second color differentthan the first color. The at least second light emitting diode structureof the plurality of light emitting diode structures may alternatively orin addition be characterized by a second flux different than the firstflux. The first color or the first flux, the second color or the secondflux and the optical cross talk between the light emitting diodes arearranged to provide a predefined light distribution and preferably apredefined color distribution in a reference plane perpendicular to anoptical axis of the light emitting diode array module. The referenceplane is arranged at a defined distance to the light emitting diodearray module.

The color of one of the LED structures may be preferably becharacterized by the color temperature, correlated color temperature andthe like. Especially the correlated color temperature may be preferredto characterize a LED module emitting white light.

Classic high-power LED structures are simple surface emitting lightsources. However, these structures are getting smaller as timeprogresses, which is mostly cost-driven. One of the features that areallowing for further cost-down is 5-sided emission. Where a conventionalLED structure would only emit from the top, a 5-sided emitter would alsoemit front the sides.

Such novel emitters have advantages in cost, but also in designflexibility. One could for example envisage a close-packed array ofthese emitters to achieve a very high-density high-flux emitter array.

Because of the 5-sided emission, light exiting the side of an emitterhas a reasonable chance of entering a neighboring LED. The lightentering its neighbor will interact with the neighboring LED which canresult in a change of color and/or a change of flux. Such a change maybe caused by phosphor interaction in the second LED structure and/orabsorption of light in the second LED structure.

An LED structure at the edge of an array will therefore be affected lessthan an LED structure in the middle of the array.

This may result in:

An array with a total flux and average color point that is differentfrom the LEDs when used in isolation.

Over the array, the flux and color will vary. Color variation over thearray is unwanted as it may result in non-uniform spot lighting.

The LED array module described above avoids or at least reduces theproblem of color (flux) variation by taking into account the influenceof neighboring LED structures in the LED array module. The LEDstructures are characterized by different (e.g. first, second, third,fourth etc.) colors or correlated color temperatures and optionallyfirst, second, third, fourth fluxes which are combined in a way that theinteraction between the LED structures is taking into account in orderto provide the predefined color point and optionally flux distribution.The predefined correlated color temperature distribution may, forexample, be a homogeneous or uniform correlated color temperaturedistribution or it may be a non-uniform color point distribution (e.g. acool white correlated color temperature in a center and a warm whitecorrelated color temperature at a border of the light distributionprovided by means of the LED array module).

The correlated colors or color temperature of the LED structures and/orthe fluxes may be chosen based on the binning of the different LEDstructures. That means that LED structures with, for example, differentcorrelated color temperatures and/or fluxes are combined, wherein thedifference of the correlated color temperatures and/or fluxes is causedby variations in the production process of the LED structures.Alternatively, LED structures with different semiconductor layers (e.g.composition of active layer) and/or different light conversion structuremay be combined in order to enable the predefined distribution of thecolor and especially the correlated color temperature and/or fluxes ofthe LED array module.

The first, second, third etc. color or correlated color temperatureand/or fluxes of the LED structures refers to the color, or correlatedcolor temperature of an isolated LED structure without any interactionwith neighboring LED structures.

At least the first light emitting diode structure of the plurality oflight emitting diode structures may be further characterized by a firstflux. At least a third light emitting diode structure of the pluralityof light emitting diode structures may be characterized by a. thirdflux. The first flux, the third flux and the optical cross talk betweenthe light emitting diodes may be arranged to provide the predefinedlight distribution in the reference plane. The third LED structure maybe the same as the second LED structure or a different LED structure.The third LED structure may be further characterized by a third color orcorrelated color temperature different than the first and/or secondcolor or correlated color temperature.

The predefined light distribution may comprise a predefined color pointtemperature distribution. The first correlated color temperature and thesecond correlated color temperature may be arranged to at least partlycompensate the optical cross talk between the light emitting diodestructures such that a homogeneity of the predefined color pointtemperature distribution is increased.

The optical cross talk between the LED structures may cause anunintended shift of the correlated color temperature of neighboring LEDstructures. This unintended shift may be compensated by providing 2, 3,4 or more LED structures with different correlated color temperatures.

The light emitting diode structures may be arranged to emit primarylight and secondary light. The primary light is characterized by a firstcenter wavelength in a first wavelength range. The secondary light ischaracterized by a second center wavelength in a second wavelengthrange. The second wavelength range is in a longer wavelength range thanthe first wavelength range. The at least first correlated colortemperature and the at least second correlated color temperature aredetermined based on a probability that a light emitting diode structurereceives primary light from one or more light emitting diode structuresencompassing the light emitting diode structure.

The probability may be determined based on a number of the lightemitting diode structures encompassing the light emitting diodestructure.

The probability that alternatively or in addition be determined based ona distance between the light emitting diode structures encompassing thelight emitting diode structure and the light emitting diode structure.

The probability may alternatively or in addition be determined based ona relative position of the light emitting diode structures encompassingthe light emitting diode structure with respect to the light emittingdiode structure.

The probability of receiving light and especially primary or secondarylight is in general determined by the illumination pattern of eachsingle LED structure and the geometric arrangement of the LED structureswithin the LED array module. Symmetry of the LED structures within theLED array module, varying distances lengths of common border betweenneighboring LED structures influence the probability that, for example,primary light is received by a light conversion structure of aneighboring (encompassing) LED structure. Furthermore, the arrangementof the LED structures may influence emission of secondary light whichmay be emitted after conversion of primary light received from aneighboring LED structure. In addition there may be optical structuresespecially at the border of a LED array module which may be arranged toreflect, for example, primary light emitted by LED structures at theborder back to the emitting LED stricture or a neighboring LED structureof the emitting LED structure. The optical structure or structures mayespecially be arranged to approximately mimic a neighboring LED. Theoptical structure may have in this case the effect that, for example,primary light emitted by a LED structure is reflected such that itappears for the emitting LED structure and neighboring LED structuresthat there is one or more LED structure at the position of the opticalstructure. The optical structure or structures provide a kind of imageof the LED structures at the border of the LED array module.

A correlated color temperature of the light emitting diode structureencompassed by the light emitting structures may be higher the higherthe probability of receiving primary light from the encompassing lightemitting diode structures is.

The probability of receiving, for example, primary light from LEDstructures by means of a light conversion structure (e.g. phosphorlayer) and the probability of conversion of this primary light tosecondary light determine the amount of additional secondary light whichis emitted by the light conversion structure of the respective LEDstructure. It may therefore be necessary to shift the correlated colortemperature of an LED structure with a high probability of emittingadditional secondary light based on the primary light received fromencompassing LED structures to higher correlated color temperatures. Thehigher correlated color temperature may be chosen such that the ratiobetween primary light and secondary light emitted by the LED structureencompassed by the other LED structures is essentially the same as aratio of the primary light and secondary light emitted by theencompassing LED structures (taking into account the cross talk betweenall neighboring LED structures).

The predefined correlated color temperature distribution may be flatwithin a defined distance from the optical axis. The first, second,third, fourth or more different correlated color temperatures of the LEDstructures may be used to extend the sector of uniform correlated colortemperature of a lighting pattern provided by a LED array structure. Thepredefined correlated color temperature distribution may in this case beflat in the reference plane around the optical axis. The different(lower) correlated color temperature of LED structures at the border ofthe array may extend the distance from the optical axis in the referenceplane in which the predefined correlated color temperature distributionis flat.

The light emitting diode array module may comprise a multitude of lightemitting diode structures arranged in a regular pattern. The regularpattern of light emitting diode structures comprises a central area anda border area. A correlated color temperature of light emitting diodestructures comprised by the border area is arranged to at least partlycompensate the optical cross talk in accordance with a correlated colortemperature distribution provided by light emitting diode structurescomprised by the central area.

The light emitting structures of the LED array module may becharacterized by, for example sub arrays with different emissioncharacteristics. The correlated color temperature of the LED arraymodule in the central area may, for example, be determined by theintensity provided by the different sub arrays of LED structures. LEDstructures comprised by the border area of the LED array module arecharacterized by different correlated color temperatures of therespective sub array in comparison to the central area in order tocompensate changes of the correlated color temperature caused by varyingoptical cross talk caused by the geometric arrangement of encompassingLED structures as described above.

According to a further aspect a lighting device is provided. Thelighting device comprises one, two, three or more light emitting diodearray modules as described above. The lighting device further comprisesat least one optical device being arranged to distribute light emittedby the at least one light emitting diode array module. The opticaldevice may be a single lens or a complex arrangement of lenses,apertures and the like.

According to a further aspect a method of emitting light with ahomogeneous color point distribution by means of a light emitting diodearray module comprising a plurality of light emitting diode structuresis provided. The method comprises the steps of:

emitting light of a first correlated color temperature by means of atleast a first light emitting diode structure of the plurality of lightemitting diode structures such that there is an optical cross talk withat least a second light emitting diode structure, emitting light of asecond correlated color temperature different than the first correlatedcolor temperature by means of at least the second light emitting diodestructure of the plurality of light emitting diode structures such thatthere is an optical cross talk with at least the first light emittingdiode structure, wherein the first correlated color temperature and thesecond correlated color temperature are arranged to at least partlycompensate the optical cross talk between the light emitting diodestructures such that a homogeneity of a predefined correlated colortemperature distribution in a reference plane perpendicular to anoptical axis of the light emitting diode array module is increased.

It shall be understood that the light emitting diode array module of anyone of claims 1-10 and the method of claim 11 have similar and/oridentical embodiments, in particular, as defined in the dependentclaims.

It shall be understood that a preferred embodiment of the invention canalso be any combination of the dependent claims with the respectiveindependent claim.

Further advantageous embodiments are defined below.

BRIEF DESCRIPTION OF THE DRAWINGS:

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

The invention will now be described, by way of example, based onembodiments with reference to the accompanying drawings.

In the drawings:

FIG. 1 shows a principal sketch of a light emitting diode structure

FIG. 2 shows a principal sketch of a light emitting diode array

FIG. 3 shows a principal sketch of a first embodiment of a LED arraymodule

FIG. 4 shows a principal sketch of a second embodiment of the LED arraymodule

FIG. 5 shows a principal sketch of a third embodiment of the LED arraymodule

FIG. 6 shows a principal sketch of a cross-section of a fourthembodiment of the LED array module

FIG. 7 shows a first embodiment of a predefined correlated colortemperature distribution

In the Figures, like numbers refer to like objects throughout objects inthe Figures are not necessarily drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS:

Various embodiments of the invention will now be described by means ofthe Figures.

FIG. 1 shows a principal sketch of a cross-section of a light emittingdiode (LED) structure 10. The LED structure 10 comprises a n-layer 3which can be electrically contacted by means of n-contact 5. The n-layer3 is followed by active layer 4. The active layer 4 may comprise aQuantum Well structure which is arranged to emit light with a wavelengthwhich is determined by the composition of the active layer (e.g.,AllnGaN). The active layer 4 is embedded or sandwiched between then-layer 3 and a p-layer 7. The p-layer 7 can he electrically contactedby means of p-contact 9. The arrangement of n-layer 3, active layer 4,p-layer 9, n-contact 5 and p-contact 9 build a LED die. There may befurther support layers which are not shown. A light conversion structure1 is attached to a top surface of the n-layer 3 which is opposite tosurface of the n-layer 3 attached to the active layer 4. The top surfaceof the n-layer 3 is the light emitting surface of the LED die. The lightconversion structure I may comprise a phosphor like a Cerium dopedphosphor garnet (YAG:Ce). The light conversion structure 1 is arrangedto convert primary light 11 (e.g. blue light) emitted by the activelayer 4 to secondary light 12 (e.g. yellow light) characterized by alonger wavelength than the primary light 11. A predefined part of theprimary light 11 passes light conversion structure 1 without beingconverted such that the LED structure emits a mixture of primary light11 and secondary light 12 (white light). The LED structure 10 isarranged to emit at least a major part of the light via a top surfaceand the side surfaces of the light conversion structure 1, wherein thetop surface is opposite to the surface of the light conversion structure1 which is attached to the n-layer 3. A LED structure 10 with arectangular or quadratic cross-section perpendicular to thecross-section shown in FIG. 1 comprises therefore five light emissionsurfaces.

Alternatively, a kind of lid comprising the phosphor material may bearranged around the LED die of the LED structure 10 such that a mixtureof primary and secondary light is emitted by means of different sides ofthe LED structure 10. Furthermore, the LED structure 10 may be embeddedin a transparent light distribution structure which is arranged to emitlight and essentially all directions of the semi-sphere in the directdirection of light emission of the LED structure 10,

FIG. 2 shows a principal sketch of a cross-section of a light emittingdiode array 30. The light emitting diode array 30 comprises a number ofLED structures 10 (three arc shown in the cross-section) attached to asubmount 20. The submount 20 comprises a submount chip 21 on which theLED structures 10 are mounted and electrical contact pads 23 by means ofwhich the n-contacts and p-contacts (not shown) of the LED structures 10can be electrically connected. The LED structures 10 emit primary (blue)light 11 and secondary (yellow) light 12. A part of the primary light 11emitted by the left and the right LED structure 10 may hit the lightconversion structure 1 of the LED structure 10 in the middle. The LEDstructure 10 in the middle therefore receives more primary light 11 fromneighboring (or encompassing) LED structures 10 than the LED structures10 at the left and at the right. The relative fraction of secondarylight emitted from the light conversion structure 1 of the LED structure10 in the middle is therefore increased. The correlated colortemperature of the LED structure 10 in the middle seems therefore to belower than the correlated color temperature of the LED structures on theleft and the right side provided that all LED structures 10 are arrangedto emit in a single arrangement, for example, white light of the samecorrelated color temperature. The same applies to the total flux emittedby the LED structures 10 because the LED 10 structure in the middleadditionally receives more secondary light than the LED structures 10 onthe left and the right side.

FIG. 3 shows a principal sketch of a top view of a first embodiment of aLED array module 30. The LED array module 30 comprises three LEDstructures 10 a, 10 b which are arranged along an axis (linear array) ina similar way as described with respect to FIG. 2. A LED structure 10 ais arranged between two LED structures 10 b. The LED structure 10a inthe middle emits white light with a higher first correlated colortemperature in order to compensate a color shift caused by primary lightemitted by the two adjacent LED structures 101) emitting white lightwith a lower second correlated color temperature in comparison to thefirst correlated color temperature. The second correlated colortemperature is chosen such that the amount of additional convertedsecondary light 12 (see FIG. 2) caused by primary light received by thelight conversion structure 1 of the LED structure 10 a in the middle isessentially compensated. The correlated color temperature distributionof the light emitting module 30 is therefore more homogeneous or uniformalong the axis of the linear array. It is clear that the selection ofthe first and the second correlated color temperature is determined bythe geometric boundary conditions such that a perfect compensation isnot possible. The same principal may be used in order to compensatevariations of the flux caused by the optical cross talk betweenneighboring LED structures 10. The flux of the LED structures 10 b atthe left and the right may, for example, be higher than the optical fluxof LED structure 10 a in the middle in order to improve homogeneity ofthe flux of LED array module 30.

FIG. 4 shows a principal sketch of a top view of a second embodiment ofthe LED array module 30. The LED array module 30 comprises a symmetricarrangement of LED structures 10 a, 10 b, 10 c, 10 d. The LED arraymodule 30 comprises two symmetry axes both crossing a center point ofthe LED array module 30. Symmetry with respect to the first symmetryaxis is in this case different than the symmetry with respect to thesecond symmetry axis. The LED structures 10 a, 10 b, 10 c, 10 d arearranged such that four LED structures 10 a with a first correlatedcolor temperature are arranged in the middle of the LED array module 30.The four LED structures 10a are encompassed by 10 LED structures 10 b,10 c, 10 d. The correlated color temperatures of the LED structures 10b, 10 c, 10 d is selected based on the relative position to neighboringLED structures 10 a, 10 b, 10 c, 10 d, the number of neighboring LEDstructures 10 a, 10 b, 10 c, 10 d and the distance(s) (the distancesmay, for example, be different in different directions) between theneighboring LED structures 10 a, 10 b, 10 c, 10 d, The geometry of thearrangement of the LED structures 10 a, 10 b, 10 c, 10 d in the LEDarray 30 determines a probability of receiving primary light fromneighboring LED structures 10 a, 10 b, 10 c, 10 d. The nearer thedistance, the more neighboring LED structures 10 a, 10 b, 10 c, 10 dencompass the respective LED structure 10 a, 10 b, 10 c, 10 d the higheris the probability to receive primary light from neighboring LEDstructures 10 a, 10 b, 10 c, 10 d. The correlated color temperature ofthe four LED structures 10 a in the middle is therefore the highest. Itis intended to provide an essentially uniform correlated colortemperature distribution across the LED array module 30 because each ofthe four LED structures 10a is encompassed by seven other LED structures10 a, 10 b, 10 c, 10 d. The second correlated color temperature of LEDstructures 10 b is lower than the correlated color temperature of the.LED structures 10 a in the center but higher than the correlated colortemperatures of LED structures 10 c, 10 b because four LED structures 10a, 10 c, 10 d encompass LED structures 10 b such that three sides of LEDstructure have overlap with sides of the encompassing LED structures 10a, 10 c, 10 d. The LED structures 10 d have a lower correlated colortemperature than LED structures 10 b but at a higher correlated colortemperature than LED structure 10 c being characterized by the lowestcorrelated color temperature of the LED array module 30.

FIG. 5 shows a principal sketch of a top view of a third embodiment ofthe LED array module 30. LED array module 30 comprises in this case twosub arrays of LED structures, which are arranged in a checkerboardpattern. The LED structures 17 of the first sub array (bright squares)are arranged to emit light of a first characteristic. The LED structuresof the second sub array (dark squares) are arranged to emit light of asecond characteristic. Each sub array 17, 18 can be controlledindependently from the other sub array. The LED structures 17 of thefirst sub array may, for example, be arranged to emit light with a firstcolor (e.g. blue). The LED structures 18 of the second sub array may,for example, be arranged to emit light with a second color (e.g yellow).The color of the light emitted by the LED array module 30 can thereforebe controlled by means of the relative intensities provided by the twosub arrays. The general problem as discussed with respect to FIGS. 2, 3and 4 remains the same. The LED array module 30 comprises a central area16 wherein the LED structures 17, 18 of the central area 16 are eachencompassed by the same number and kind of LED structures 17, 18. TheLED array module 30 further comprises a border area 15 in which thenumber of encompassing LED structures 17, 18 depends on the positionwithin the border area 15. The color of the LED structures 17, 18 of theborder area 15 are therefore different than the color of the LEDstructures 17, 18 of the corresponding central area 16 in order tocompensate the different optical crosstalk between the LED structures17, 18. The color of the LED structures 17, 18 of the border area 15essentially depends on the number of LED structures 17, 18 encompassingthe respective LED structure 17, 18. The area of the LED array module 13appearing to emit light of the same color and correlated colortemperature is thus increased. The border area 15 and the central area16 are separated by a small gap in FIG. 5 in order to simplifyidentification of LED structures 17, 18 of the central area 16 and theborder area 15. There is no such a gap in the real LET) array module 30.

FIG. 6 shows a principal sketch of a cross-section of a fourthembodiment of the LED array module 30. The LED array module comprises anarray of 5×6 LED structures 10. The cross section shows six LEDstructures 10 in the third of the five lines of LED structures 10 whichare arranged in a regular quadratic pattern. The LED structures 10 areattached to a submount 20 comprising a submount chip 21 and electricalcontact pads 23 as discussed with respect to FIG. 2. The LED array,module 30 comprises an optical axis 50 which is arranged in the middleof the 5×6 LED structures 10. Each of the LED structures 10 emits mixedlight 13 comprising primary light 11 and secondary light 12 as discussedwith respect to FIG. 2. The mixed light 13 overlaps in reference plane40 which may, for example, be arranged in a distance preferably between5 mm and 10 mm in order to detect the impact of the LED structures 10comprised by the LED module 30. The correlated color temperature of theLED structures 10 of the central area of the LET) array module 30 ishigher in comparison to the correlated color temperature of the LEDstructures 10 of the border area of the LED array module 30. The LEDstructures 10 at the four corners of the LED array module 30 arecharacterized by the lowest correlated color temperature because theseLED structures 10 are encompassed by the lowest number of encompassingLED structures 10.

FIG. 7 shows the predefined correlated color temperature distribution 65of the LED array module 30 shown in FIG. 6 along an axis of referenceplane 40. The axis crosses the optical axis 50 and is arranged along theline defined by the LED structures 10 shown in FIG. 6. The abscissa 61shows the distance to the optical axis 50 in the reference plane 40 andthe ordinate 62 shows the correlated color temperature along the axis inthe reference plane 40. The predefined correlated color temperaturedistribution 65 is essentially constant or flat within a predefinedrange around the optical axis 50 in the reference plane 40. Thepredefined range within the reference plane 40 is determined by theillumination pattern provided by each LED structure 10, the geometricorientation of the LED structures 10 within the LED array module 30 andthe compensation of the optical cross talk by means of the differentcorrelated color temperature of LED structures 10 in the border area ofthe LED array module 30.

Although the disclosure mainly speaks of correlated color temperature todescribe the color of LED structures 10, the invention is not limited tocolors of a black body radiator.

A person skilled in the art will understand that the invention holds forcolor compensation in the full color space. Typically, the colorsmentioned in the disclosure will be along the phosphor load line(s),i.e. the colors one can create by changing the concentration of phosphorin light conversion structure I of the corresponding LED structure 10.

While the invention has been illustrated and described in detail in thedrawings and the foregoing description, such illustration anddescription are to be considered illustrative or exemplary and notrestrictive.

From reading the present disclosure, other modifications will beapparent to persons skilled in the art. Such modifications may involveother features which are already known in the art and which may be usedinstead of or in addition to features already described herein.

Variations to the disclosed embodiments can be understood and effectedby those skilled in the art, from a study of the drawings, thedisclosure and the appended claims, in the claims, the word “comprising”does not exclude other elements or steps, and the indefinite article “a”or “an” does not exclude a plurality of elements or steps. The mere factthat certain measures are recited in mutually different dependent claimsdoes not indicate that a combination of these measures cannot be used toadvantage.

Any reference signs in the claims should not be construed as limitingthe scope thereof.

LIST OF REFERENCE NUMERALS:

-   1 light conversion structure-   3 n-layer-   4 active layer-   5 n-contact-   p-layer-   p-contact-   light emitting diode (LED) structure-   10 a LED structure with first correlated color temperature-   10 b LED structure with second correlated color temperature-   10 c LED structure with third correlated color temperature-   10 d LED structure with fourth correlated color temperature-   11 primary light-   12 secondary light-   13 mixed light-   15 light emitting diode structure of border area-   16 light emitting diode structure of central area-   17 LED structure of first sub array-   18 LED structure of second sub array-   20 submount-   21 submount chip-   23 electrical contact pads-   30 light emitting diode (LED) array module-   40 reference plane-   50 optical axis-   61 distance to optical axis in reference plane-   62 correlated color temperature in reference plane-   65 correlated color temperature distribution in reference plane

1. An apparatus, comprising: a plurality of light-emitting diode (LEDs)arranged as an LED array, the plurality of LEDs being distributedbetween a central group of LEDs and a border group of LEDs thatsurrounds the central group of LEDs, the central group of LEDs includingcentral blue LEDs that are configured to emit central blue light andcentral yellow LEDs that are configured to emit central yellow lightsuch that, when observed at a reference plane separated from the LEDarray, the central blue light and the central yellow light combine toappear as central white light having a central correlated colortemperature, the border group of LEDs including border blue LEDs thatare configured to emit border blue light and border yellow LEDs that areconfigured to emit border yellow light such that, when observed at thereference plane, the border blue light and the border yellow lightcombine to appear as border white light having a border correlated colortemperature that is different from the central correlated colortemperature.
 2. The apparatus of claim 1, wherein: the central blue LEDsand the central yellow LEDs are arranged in a checkerboard pattern inthe LED array; and the border blue LEDs and the border yellow LEDs arearranged in a checkerboard pattern in the LED array.
 3. The apparatus ofclaim 1, wherein: each of the central blue LEDs is configured to emitlight having a same central blue intensity; each of the central yellowLEDs is configured to emit light having a same central yellow intensity;each of the border blue LEDs is configured to emit light having a sameborder blue intensity; each of the border yellow LEDs is configured toemit light having a same border yellow intensity; and a ratio of thecentral blue intensity to the central yellow intensity differs from aratio of the border blue intensity to the border yellow intensity. 4.The apparatus of claim 1, wherein at least some of the LEDs of the LEDarray are monolithic devices disposed on a single substrate.
 5. Theapparatus of claim 1, wherein: the LED array is a two-dimensional array;each LED in the central group is fully surrounded by adjacent LEDs inthe LED array; and each LED in the border group is only partiallysurrounded by adjacent LEDs in the LED array.
 6. The apparatus of claim1, wherein: the array of LEDs is a two-dimensional rectilinear array;each LED in the central group is surrounded by four directly adjacentLEDs and four diagonally adjacent LEDs in the LED array; and each LED inthe border group is surrounded by fewer than four directly adjacent LEDsor fewer than four diagonally adjacent LEDs in the LED array.
 7. Theapparatus of claim 1, wherein: the LED array is a two-dimensional arraythat extends in a first plane that is generally parallel to thereference plane; each LED in the array is configured to emit light froma first emission surface oriented generally parallel to the first planeand from at least one second emission surface oriented substantiallyorthogonal to the first emission surface; and the LEDs of the array arearranged such that the at least one second emission surface of an LED ispositioned to receive light from a second emission surface of at leastanother LED in the array.
 8. The apparatus of claim 7, wherein lightemitted from a second emission surface of a first. LED of the array isconfigured to interact with a phosphor of a second LED of the array. 9.The apparatus of claim 7, wherein central blue light emitted from asecond emission surface of a first central blue LED is configured to beabsorbed by a phosphor of a first central yellow LED.
 10. The apparatusof claim 7, wherein central blue light emitted from a second emissionsurface of a first central blue LED is configured to be absorbed by aphosphor of a first border yellow LED.
 11. The apparatus of claim 7,wherein border blue light emitted from a second emission surface of afirst border blue LED is configured to be absorbed by a phosphor of afirst border yellow LED.
 12. The apparatus of claim 7, wherein borderblue light emitted from a second emission surface of a first border blueLED is configured to be absorbed by a phosphor of a first central yellowLED.
 13. A method for providing light, comprising: electrically poweringa plurality of light-emitting diode (LEDs) arranged as an LED array, theplurality of LEDs being distributed between a central group of LEDs anda border group of LEDs that surrounds the central group of LEDs, thecentral group of LEDs including central blue LEDs and central yellowLEDs, the border group of LEDs including border blue LEDs and borderyellow LEDs; emitting central blue light from the central blue LEDs;emitting central yellow light from the central yellow LEDs such that,when observed at a reference plane separated from the LED array, thecentral blue light and the central yellow light combine to appear ascentral white light having a central correlated color temperature;emitting border blue light from the border blue LEDs; and emittingborder yellow light from the border yellow LEDs such that, when observedat the reference plane, the border blue light and the border yellowlight combine to appear as border white light having a border correlatedcolor temperature that is different than the central correlated colortemperature.
 14. The method of claim 13, wherein: the central blue LEDsand the central yellow LEDs are arranged in a checkerboard pattern inthe LED array; and the border blue LEDs and the border yellow LEDs arearranged in a checkerboard pattern in the LED array.
 15. The method ofclaim 13, wherein: the central blue LEDs emit light having a samecentral blue intensity; the central yellow LEDs emit light having a samecentral yellow intensity; the border blue LEDs emit light having a sameborder blue intensity; the border yellow LEDs emit light having a sameborder yellow intensity; and a ratio of the central blue intensity tothe central yellow intensity differs from a ratio of the border blueintensity to the border yellow intensity.
 16. The method of claim 13,wherein at least some of the LEDs of the LED array are monolithicdevices disposed on a single substrate.
 17. The method of claim 13,wherein: the LED array is a two-dimensional array; each LED in thecentral group is fully surrounded by adjacent LEDs in the LED array; andeach LED in the border group is only partially surrounded by adjacentLEDs in the LED array.
 18. The method of claim 13, wherein: the array ofLEDs is a two-dimensional rectilinear array; each LED in the centralgroup is surrounded by four directly adjacent LEDs and four diagonallyadjacent LEDs in the LED array; and each LED in the border group issurrounded by fewer than four directly adjacent LEDs or fewer than fourdiagonally adjacent LEDs in the LED array.
 19. An apparatus, comprising:a plurality of light-emitting diode (LEDs) arranged as a two-dimensionalrectilinear LED array, the plurality of LEDs being distributed between acentral group of LEDs and a border group of LEDs that surrounds thecentral group of LEDs, each LED in the central group being surrounded byfour directly adjacent LEDs and four diagonally adjacent LEDs in the LEDarray, each LED in the border group being surrounded by fewer than fourdirectly adjacent LEDs or fewer than four diagonally adjacent LEDs inthe LED array, the central group of LEDs including central blue LEDsthat are configured to emit central blue light and central yellow LEDsthat are configured to emit central yellow light such that, whenobserved at a reference plane separated from the LED array, the centralblue light and the central yellow light combine to appear as centralwhite light having a central correlated color temperature, the centralblue LEDs and the central yellow LEDs being arranged in a checkerboardpattern in the LED array, the border group of LEDs including border blueLEDs that are configured to emit border blue light and border yellowLEDs that are configured to emit border yellow light such that, whenobserved at the reference plane, the border blue light and the borderyellow light combine to appear as border white light having a bordercorrelated color temperature that is different than the centralcorrelated color temperature, the border blue LEDs and the border yellowLEDs are arranged in a checkerboard pattern in the LED array.
 20. Theapparatus of claim 19, wherein: the LED array is a two-dimensional arraythat extends in a first plane that is generally parallel to thereference plane; each LED in the array is configured to emit light froma first emission surface oriented generally parallel to the first planeand from at least one second emission surface oriented substantiallyorthogonal to the first emission surface; the LEDs of the array arearranged such that the at least one second emission surface of an LED ispositioned to receive light from a second emission surface of at leastanother LED in the array; light emitted from a second emission surfaceof a first LED of the array is configured to interact with a phosphor ofa second LED of the array; central blue light emitted from a secondemission surface of a first central blue LED is configured to beabsorbed by a phosphor of a first central yellow LED; central blue lightemitted from a second emission surface of a first central blue LED isconfigured to be absorbed by a phosphor of a first border yellow LED;border blue light emitted from a second emission surface of a firstborder blue LED is configured to be absorbed by a phosphor of a firstborder yellow LED; and border blue light emitted from a second emissionsurface of a first border blue LED is configured to be absorbed by aphosphor of a first central yellow LED.